Directing attention to FIG. 1, the IEEE 1394a standard defines communication protocols between nodes 2 on a computer network 4. Nodes 2 can be personal computers, workstations, or other computing devices. Each node has a PHY 6, which facilitates communication between the nodes and other nodes in network 4. PHY 6 has a plurality of ports so that multiple connections can be made to node 2. Nodes 2 can be connected by cable 8, or other suitable communication medium, to implement computer network 4. It is one of the goals of the 1394a standard to implement a protocol that treats all communication media connecting nodes 2 collectively as bus 8. To achieve this objective, a tree identification process is executed on nodes 2.
The tree identification process is executed in a distributed manner among the nodes to configure network 4 in a tree structure among nodes 2. The tree identification process executed on each node establishes a hierarchy among nodes 2 such that each connection between two nodes 2 defines one node as the parent of the other node and the other node as the child of the first node. A node may thus be parent to zero or more children, and each node has at most one parent. On each node 2, a flag on each port in PHY 6 indicates the peer node as either a parent or a child. A root node 2-1 eventually is determined to be a node that has only children and no parent. By establishing a hierarchy among nodes 2, the communication protocols of the IEEE1394a standard are able to function properly. The root node 2-1 has particular responsibilities, such as acting as cycle master and issuing cycle start packets. This function is essential to isochronous operation, which, in turn, is essential to the use of the IEEE1394a standard in consumer digital audio-visual applications among others. When a node has identified all connections to its PHY 6 as being connections to children with the exception of one connection, it is assumed that the remaining, unidentified connection points to a potential parent node.
A problem occurs when a user incorrectly installs a node in network 4. For the tree identification process (and therefore network 4) to function properly there needs to be one less connection cable between nodes than the number of nodes present in network 4. However, as most devices that are compatible as nodes within network 4 are sold with an accompanying cable, quite often the user simply connects the new node using the cable as an addition to bus 8. This violates the requirement of bus 8 having one less connection cable than the number of nodes in network 4.